Communication between base stations includes backhaul (back haul) link communication and fronthaul link communication. Backhaul refers to a network from a base station controller to a serving gateway or a mobility management entity, and fronthaul refers to a network from a baseband processing unit (BBU) of an antenna to the base station controller. Backhaul and fronthaul impose very high requirements on reliability. For example, a packet error rate (PER) of backhaul needs to be 10−6, and a packet error rate of fronthaul needs to be 10−8. In addition, the backhaul link communication and the fronthaul link communication are usually deployed in a high frequency, and a space loss of the high frequency is very large. Therefore, a higher requirement is imposed on reliability of transmission in a high-frequency environment.
Currently, transmission reliability is improved mainly by using a diversity solution. A basic idea of diversity is: If a plurality of independently fading signals can be transmitted, from the perspective of statistics, fading of a combined signal is much lower than fading of each signal. Under the assumption of independent fading, when some signals fade deeply, fading of some other signals may be relatively slight, and a probability that signals deeply fade simultaneously is very low. Therefore, a probability that a combined signal deeply fades is greatly reduced. The diversity solution includes space time coding (STC), cyclic delay diversity (CDD), antenna switching diversity, and the like. A diversity solution combining space frequency block coding (SFBC) and frequency switched transmit diversity (FSTD) is often used in Long Term Evolution (LTE). As shown in FIG. 1, FIG. 1 shows an SFBC diversity solution in LTE. First, scrambling processing, modulation processing, processing of an SFBC encoder, processing of a resource element mapper, and processing of an orthogonal frequency division multiplexing (OFDM) signal generator are sequentially performed on a to-be-sent signal, and finally, the data is sent by using antenna ports. For an SFBC encoder with two transmit antennas, assuming that data symbols flowing to the SFBC encoder are X2k and X2k+1, X2k is transmitted on a first subcarrier on antenna 1, and X2k+1 is transmitted on a second subcarrier, while −X2k+1 is transmitted on a first subcarrier on antenna 2, and X2k is transmitted on a second subcarrier. ( )* represents conjugate of a complex number. In the diversity solution, repeated data is sent in a frequency and space, to improve transmission reliability, thereby improving reliability of receiving information by user equipment. However, for a high-frequency environment having a very great space loss, an antenna gain of the diversity solution is relatively low, the space loss cannot be overcome, and as a result, transmission reliability is severely affected.